A process of manufacturing semiconductor substrates (hereinafter, simply referred to as “substrates”) conventionally involves various types of processing performed by a substrate processing apparatus on a substrate having an insulation film such as an oxide film. One example is cleaning processing for removing particles or the like that adhere to the surface of a substrate by supplying a cleaning liquid to the substrate surface.
International Publication No. WO 2007/132609 (Document 1) discloses a substrate cleaning apparatus that is provided with a droplet removing nozzle disposed in the vicinity of a process nozzle located at a standby position outside a substrate, and in which gas is blown from the droplet removing nozzle against the process nozzle in order to prevent unintended liquid dripping from the process nozzle.
Japanese Patent Application Laid-Open No. 2001-232250 (Document 2) proposes a technique for use in a membrane forming apparatus for forming a membrane on a substrate by ejecting a coating liquid onto the substrate. With the technique, a cleaning liquid is ejected to outlets of a coating liquid ejection nozzle to remove contaminants adhering to the outlets, and then, the cleaning liquid ejected to the outlets is sucked to be discharged from the outlets as well as to dry the outlets.
Japanese Patent Application Laid-Open No. 2012-43949 (Document 3) proposes a technique for use in a coating device for forming a coating film on a substrate by applying a processing liquid to the substrate. With the technique, when a nozzle for ejecting a processing liquid from a slit outlet is on standby, the processing liquid in a flow passage of the nozzle is transformed into a solvent of the processing liquid and retained in the form of a solvent. Document 3 also proposes to immerse the tip of the nozzle, in which the processing liquid has been transformed to the solvent, into a solvent retained in a casing.
Japanese Patent Application Laid-Open No. 2006-302934 (Document 4) discloses a technique for use in a liquid treatment apparatus, in which, during standby of a processing liquid supply nozzle, the processing liquid in the nozzle is sucked to form an air layer in the vicinity of an outlet in a flow passage of the nozzle, and the processing liquid is further sucked in a state where the tip of the nozzle is immersed in a solvent of the processing liquid to form a solvent layer on the outer side of the air layer.
Incidentally, as one example of the substrate processing apparatuses, there is known to be an apparatus for processing a substrate by ejecting fine droplets of a processing liquid toward the substrate from a plurality of fine outlets provided in an ejection head. Such an apparatus may suffer from clogging of the outlets due to, for example, drying of the outlets during standby of the ejection head. It is thus conceivable to apply the processing liquid in the vicinity of the outlets to prevent drying of the outlets. There is, however, the possibility that the processing liquid adhering to the ejection head may drop and adhere to a substrate (so-called “liquid dripping”) when the use of the ejection head is resumed.